I normally try not to put any fat down our sink and when I do, I make sure I
use plenty of detergent & hot water but I was a bit horrified when our
drains were dug up (for an extension, not for blockage) to see this.

http://www.zen31010.zen.co.uk/images/yuck.jpg

I'm going to be a *lot* more careful in the future but given that everything
is getting revamped, I was wondering about a grease trap for the drain. A
quick seach just seems to throw up catering sized traps. Are there any
smaller ones for domestic use?

Tim